(1) Field of the Invention
This invention relates to module movers which are well known pieces of equipment used in the cotton industry. Those with ordinary skill in the art are designers and makers of cotton module movers.
(2) Description of the Related Art
The module mover is used to load, transport, and unload cotton modules. These modules are compressed parallelepipedon masses of harvested cotton with dimensions in excess of seven feet by seven feet by thirty-five feet.
As cotton is harvested, it is compressed by a module builder into these modules which are deposited on the ground when compaction is completed. The modules are compacted to a density which allows them to be free standing and self-supporting. That is to say, when they are left in the field after being compacted, the modules retain their shape until being retrieved by a module mover.
The module mover has a tilting cargo bed with dimensions sufficient to accommodate the compressed module. To retrieve modules, the mover is driven into a field to the location where a module has been deposited by the module builder. Upon arriving at the location of the module, the bed of the mover is tilted, typically by hydraulic means, so that the back of the bed is at ground level. The back of the bed is then positioned against the base of the module at one of the module's ends. The tilted configuration is referred to as the loading and unloading position; hereinafter, loading position and unloading position will be used interchangeably.
The loading of the module is facilitated by the use of a live floor in the bed of the mover. The live floor typically consists of a series of chains that run the length of the bed and support the weight of the cotton module.
Loading the module is accomplished by backing the module mover under the module. As the mover progresses backward and under the module, that portion of the module which is loaded and above the mover is supported upon the live floor in the bed of the mover. When the module is completely loaded and totally supported upon the bed of the mover, the bed is then tilted back into the horizontal transporting position.
The module movers presently used in the cotton industry are supported upon tires, track units, and steel wheels during loading and unloading. Tires are located near the middle of the cargo bed's length and support most of the weight of the mover when it is transporting the modules with the cargo bed in the horizontal position. The tires also support a portion of the weight of the module mover when it is loading and unloading a module. The track units are located near the back of the bed and contact the ground and support the mover only when the bed is in the loading position. The steel wheels are attached to the bed frame behind the track units; and like the track units, the steel wheels support a portion of the weight of the mover during loading and unloading. In addition to being weight bearing supports, the steel wheels keep the back of the tilted bed positioned at the base of the module during loading and unloading. It is important that the leading edge of the back of the bed remain at or very near the interface between the cotton module and the ground on which the module is resting during loading and unloading.
The typical design of the mover permanently positions the track units so that the flat track-to-ground engaging portion of the track units is on a line which is tangent to the back steel wheels and the transporting tires. This line should be nearly horizontal when the bed is in the tilted position. The tires, track units, and wheels are designed to all contact the ground when the bed is in the tilted position.
The problem with this design is that the ground upon which loading and unloading takes place rarely provides a flat horizontal surface for the tires, track units, and wheels to engage. Since these three structures are rigidly fixed relative to the bed of the mover, they do not adjust to accommodate variations in the ground's surface. As a result, contact is made only with the high point, or points, along the line tangent to the bottom of the three structures.
The drawbacks encountered because the components are rigidly fixed to the mover are accentuated by the unevenness of the ground on which loading and unloading typically takes place. The ground is also often soft and muddy due to low compaction and high moisture content. The result is that traction is difficult to achieve between the driving components (the driving components are the track units; the tires are not used to drive the mover during loading and unloading, they merely roll as the track units pull the mover across the ground) and the ground because there is less than complete contact between the bottoms of the track units and the ground. Additionally, there is rarely an even distribution of the weight of the mover to the several supporting structures because the ground is softer under certain areas of the mover and offers differing degrees of resistance to the downward force of the weight of the mover. When the track units are above soft or muddy areas while the tires and wheels are on solid ground, the mover is not able to achieve the required traction to propel the mover along the ground and load a module.
One recent embodiment of the module mover includes track units which have been modified so that they are not rigidly fixed to the bottom of the mover. The track units are instead connected to the mover by movable legs which allow vertical extension of the track units below the mover. The movement is accomplished by placing a resilient air bag between the track units and the mover and applying equal air pressure to the bag. This allows the track units to extend independently and permits an even distribution of the mover's weight to each track unit as long as sufficient resistance from the soil is encountered before the bag reaches maximum expansion. The extension of the legs which these air bags are able to produce is limited and they do not have the ability to retract the track units up near the bottom of the mover when the track units are not needed.
Another disadvantage of the above described mover is that the track units and live floor are driven by a common hydraulic motor. The result is that during loading or unloading the track units may experience slippage so that the mover has not traveled a horizontal distance, with respect to the ground, equal to the horizontal movement of the track-to-ground engaging portion of the track units. Because the track units and the live floor are driven by the same motor, the floor will continue to move with a horizontal component equal to the horizontal movement of the track-to-ground engaging portion of the track unit, not the actual horizontal movement of the mover. This may result in the pulling apart of the module because the mover is not moving under the module at a sufficient rate to accommodate the rate at which the live floor is attempting to load the module.